Oil field operators dedicate significant resources to improve the recovery of hydrocarbons from reservoirs while reducing recovery costs. To achieve these goals, production engineers both monitor the current state of the reservoir and attempt to predict future behavior given a set of current and/or postulated conditions. The monitoring of wells by production engineers, sometimes referred to as well surveillance, involves the regular collection and monitoring of measured near-wellbore production data from within and around the wells. Such data may be collected using sensors embedded behind the well casing and/or from measurement devices introduced into the well with the production tubing. The data may include, but is not limited to, water and oil cuts, fluid pressure and fluid flow rates, and is generally collected at a fixed, regular interval (e.g., once per minute) and monitored in real-time by field personnel. As the data is collected, it is generally archived into a database.
In addition to monitoring conditions within the well, the systems used to lift produced fluids to the surface are also monitored. Such monitoring ensures that the systems are functioning as close to their optimal operating point as possible or practical, and that failures are detected and resolved promptly. One such type of system used is a gas lift (GL) system. Mandrels of the GL system are generally mounted along the production tubing and lowered into the well's production casing together with the tubing. Gas is introduced into the annular region between the casing and the tubing under pressure, and valves positioned along and/or within the mandrel allow the gas to be introduced into the fluid flow within the production tubing. GL systems help lift the product to the surface by reducing the density of the fluid (and thus the downhole pressure), which accelerates the movement of fluids from the formation through the perforations in the casing and up the production tubing.
Downhole sensors, if installed, collect and transmit data to the surface (e.g., via cables to the surface and/or wirelessly). The data may include, but is not limited to, injected gas lift pressure and temperature, and produced fluid pressure and temperature. Although the data provided enables monitoring of the performance of a GL system, determining the underlying cause of a failure or a variation in the performance of GL system is a more complicated task. A given GL system failure or performance variation can have numerous causes and operators strive to identify the cause of such issues quickly to reduce any resulting downtime or reduced production. While experienced petroleum/well surveillance personnel may rely on their personal experience to diagnose and resolve such issues, a more automated approach based on a broader information base offers the possibility of diagnosing issues and providing more optimal solutions in a shorter period of time.
It should be understood that the drawings and corresponding detailed description do not limit the disclosure, but on the contrary, they provide the foundation for understanding all modifications, equivalents, and alternatives falling within the scope of the appended claims.